Method and apparatus for cutting tubular goods

ABSTRACT

A method and apparatus for down-hole cutting of pipe, such as casing, production tubing and other tubular goods. The apparatus has a central mandrel, retractable blades and opposing helical cam sleeves, and can be conveyed into a well and actuated via slickline or other non-conductive wireline. When the apparatus is positioned at a desired down-hole position relative to the pipe to be cut, the blades are extended radially outward to contact the pipe. Axial force applied to the opposing helical cam sleeves transfers torque to the blades which, in turn, rotate and cut the pipe. After the pipe is cut, the blades are retracted, and the apparatus can be retrieved from the well.

CROSS REFERENCES TO RELATED APPLICATIONS

Priority of U.S. Provisional Patent Application Ser. No. 61/314,208 filed Mar. 16, 2010, incorporated herein by reference, is hereby claimed.

STATEMENTS AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

None

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to a method and apparatus for cutting tubular goods in oil and/or gas wells. More particularly, the present invention pertains to a method and apparatus for mechanically cutting pipe in oil and/or gas wells including, but not limited to, drill pipe, casing, production tubing and other tubular goods. More particularly still, the present invention pertains to a method and apparatus for cutting pipe in oil and/or gas wells using slickline or other non-conductive wireline.

2. Description of the Prior Art

Oil and gas wells are typically drilled using drilling rigs or other similar systems to create substantially cylindrical boreholes that extend downward into the earth's crust. After a well has been drilled to a desired depth, large diameter pipe commonly referred to as casing is frequently installed into a well and cemented in place. Thereafter, production tubing is often run into a well, concentrically inside the casing, in order to provide a conduit for the flow of oil and/or gas production from an underground reservoir to the earth's surface.

After hydrocarbon reserves in a well have been depleted, the well must eventually be plugged and abandoned and the well site restored to its original condition. Generally, surface equipment must first be removed from a depleted well. Thereafter, as much production tubing and casing as possible is typically retrieved from a well; in many cases, such recovered tubular goods can be reused in other wells or sold for salvage. However, because the pipe—and especially the casing—can be cemented or otherwise lodged in place, blades or other cutting devices are frequently needed to cut the pipe at a desired depth in the well prior to removal. After desired down-hole cut(s) are made, pipe is typically pulled out of the well from the surface.

Drilling rigs and smaller work-over rigs are frequently used for this purpose: a rig's rotary equipment can be utilized to actuate blades and/or other cutting equipment in order to make down-hole pipe cuts, while a rig's derrick and draw works can be used to pull tubular goods from a well. However, such rigs can be expensive to use for abandonment operations. Such rigs can also be difficult and expensive to mobilize to and from a well location.

Thus, there is a need for a device for mechanically cutting tubular goods in oil and/or gas wells, especially wells drilled from offshore platforms or other marine structures, that is safer and more effective than existing pipe cutting systems. Although said apparatus should be capable of being conveyed into a well via tubing or electric line, the apparatus should be beneficially conveyed into a well and actuated via slickline. The pipe cutting apparatus should also be convenient to transport, easy to use and environmentally friendly.

SUMMARY OF THE INVENTION

The present invention comprises a method and apparatus for mechanical down-hole cutting of tubular goods (such as, for example, casing, production tubing and other pipe) in wells, including oil and/or gas wells. Although the apparatus of the present invention can be conveyed into a well and actuated via tubing or electric line, it can also be conveyed and operated using non-conductive braided line or slickline (that is, wireline that does not permit the flow of electricity through such line).

Although the pipe cutter assembly of the present invention can be used in many different applications requiring the down-hole cutting of pipe or other tubular goods, it is particularly beneficial for plugging and abandonment operations, as well as pipe recovery operations. The pipe cutter assembly of the present invention is compact, manually actuated and can be operated by a single person. As a result, no explosives or chemicals are required, thereby allowing the pipe cutter assembly of the present invention to be stored and transported without any special handling or permitting requirements. Further, the pipe cutter assembly makes a clean cut, which is particularly desirable during pipe recovery and other applications.

In most instances, a “trial run” (for example, using a gauge ring and/or a junk basket) is first made in order to determine that the necessary clearance exists for the cutting assembly of the present invention to reach a desired depth. Assuming that the trial run is successful, the cutting assembly can be conveyed into the well. In the preferred embodiment, the pipe cutter assembly of the present invention has a threaded connection at its upper end, and can be threadably connected to slickline. The cutting assembly is then lowered downhole to a desired depth where a cut is to be made.

Once the tool is in place, tension can be applied to the pipe to be cut (for example, using a hammer system which is typically included with most wireline and slickline units). After pipe is cut as more fully described herein, the apparatus of the present invention is reeled up via wireline, thus contracting cutting blades. Thereafter, the apparatus can be quickly and easily pulled out of the well.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of the preferred embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, the drawings show certain preferred embodiments. It is understood, however, that the invention is not limited to the specific methods and devices disclosed. Further, dimensions, materials and part names are provided for illustration purposes only and not limitation.

FIG. 1 depicts a side perspective view of the pipe cutting assembly of the present invention in a pinned, extended configuration.

FIG. 2 depicts a side perspective view of the pipe cutting assembly of the present invention in a pinned, extended configuration, rotated 180 degrees from the view depicted in FIG. 1.

FIG. 3 depicts an exploded view of the pipe cutting assembly of the present invention.

FIG. 4A depicts a side sectional view of an upper portion of the cutting assembly of the present invention in a pinned, extended configuration.

FIG. 4B depicts a side sectional view of a lower portion of the cutting assembly of the present invention in a pinned, extended configuration.

FIG. 5 depicts a side perspective view of the pipe cutting assembly of the present invention in an unpinned, collapsed configuration.

FIG. 6 depicts a side perspective view of the pipe cutting assembly of the present invention in an unpinned, collapsed configuration, rotated 180 degrees from the view depicted in FIG. 5.

FIG. 7A depicts a side sectional view of an upper portion of the cutting assembly of the present invention in an unpinned, collapsed configuration along line 7-7 of FIG. 5.

FIG. 7B depicts a side sectional view of a lower portion of the cutting assembly of the present invention in an unpinned, collapsed configuration along line 7-7 of FIG. 5.

FIG. 8 depicts a sectional view of retracted blades of the cutting assembly of the present invention along line 8-8 of FIG. 4B.

FIG. 9 depicts a detailed sectional view of an upper shear pin highlighted in FIG. 4A.

FIG. 10 depicts a detailed sectional view of a center shear pin highlighted in FIG. 4A.

FIG. 11 depicts a detailed sectional view of a lower shear pin highlighted in FIG. 4A.

FIG. 12 depicts a sectional view of extended blades of the cutting assembly of the present invention along line 12-12 of FIG. 7B.

FIG. 13 depicts a detailed sectional view of a portion of sheared upper pin highlighted in FIG. 7A.

FIG. 14 depicts a detailed sectional view of portions of upper and middle shear pins highlighted in FIG. 7A.

FIG. 15 depicts a detailed sectional view of lower shear pin highlighted in FIG. 7A.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Referring to the drawings, FIG. 1 depicts a side perspective view of pipe cutting assembly 100 of the present invention in a pinned, extended configuration. Pipe cutting assembly 100 comprises elongate central mandrel 10 which, in the preferred embodiment, has upper threads 11 and an upper body section 15 having a substantially square outer profile.

Elongate central mandrel 10 is slidably disposed within axial bore 3 of cap member 1. In the configuration depicted in FIG. 1, elongate central mandrel 10 is secured in place via upper shear pin 120. Cap member 1 is connected to upper helical cam sleeve 80 (having lower curved helical surface 81) which is secured in place using middle shear pin 130. Lower helical cam sleeve 90 (having upper curved helical surface 91) is disposed below upper helical cam sleeve 80 and is secured in place using lower shear pin 140. In the configuration depicted in FIG. 1, lower curved helical surface 81 of upper cam sleeve 80 partially contacts upper helical surface 91 of lower cam sleeve 90.

Outer cutter housing 50 having at least one blade slot 51 extending through said housing 50 is connected to lower helical cam sleeve 80. In the preferred embodiment, said at least one blade slot 51 is oriented substantially perpendicular to the longitudinal axis of said outer cutter housing 50. Lower outer housing 40 having bottom bull nose profile 41 is connected to outer cutter housing 50.

Referring to the drawings, FIG. 2 depicts a side perspective view of the pipe cutting assembly of the present invention in a pinned configuration, rotated 180 degrees from the view depicted in FIG. 1. Elongate central mandrel 10 has upper threaded connection 11 and an upper body section 15 having a substantially square outer profile. Elongate central mandrel 10 is slidably received within axial bore 3 of cap member 1. Cap member 1 is connected to upper helical cam sleeve 80 having lower curved helical surface 81. Lower helical cam sleeve 90 having upper curved helical surface 91 is disposed below upper helical cam sleeve 80. Outer cutter housing 50 having at least one blade slot 51 extending through said housing 50 is connected to lower helical cam sleeve 80, while lower outer housing 40 having bottom bull nose profile 41 is connected to outer cutter housing 50.

With pipe cutting apparatus 100 in the pinned, extended configuration depicted in FIG. 2, a gap is formed between (a portion of) lower curved helical surface 81 of upper helical cam sleeve 80, and (a portion of) upper curved helical surface 91 of lower helical cam sleeve 90. Lower stem guide bushing 60 and upper stem guide bushing 70 can be observed in FIG. 2 through such gap formed between helical cam members 80 and 90. In the preferred embodiment, elongate central member 10 is concentrically disposed within aligned central bores of lower stem guide bushing 60 and upper stem guide bushing 70, respectively. Said stem guide bushings 60 and 70 are, in turn, both concentrically disposed within upper helical cam sleeve 80 and lower helical cam sleeve 90.

In the preferred embodiment of the present invention, upper helical cam sleeve 80, lower helical cam sleeve 90, upper stem guide bushing 70, lower stem guide bushing 60, outer blade housing 50 and bottom housing 40 all have a plurality of radial grooves extending substantially around the circumference of said components. Said grooves can be optionally filled with grease or other beneficial lubricant, which can improve lubricity during the process of running in or out of a well with cutting assembly 100.

FIG. 3 depicts an exploded view of pipe cutting assembly 100 of the present invention comprising the following components:

-   -   Cap member 1 having threads 5, central bore 3, head section 4         and transverse pin bore 2. In the preferred embodiment, central         bore 3 of cap member 1 has a substantially square shape, while         transverse pin bore is oriented substantially perpendicular to         central bore 3.     -   Upper stem guide bushing 70 having central bore 73, ring member         72 and lower threads 71.     -   Upper helical cam sleeve 80 having central bore 83, upper         threads 84, transverse pin bore 82 and lower curved helical end         surface 81.     -   Lower helical cam sleeve 90 having central bore 93, lower         threads 94 (not visible in FIG. 3), transverse pin bore 92 and         upper curved helical end surface 91.     -   Lower stem guide bushing 60 having central bore 63, ring member         62 and upper threaded connection 61 with threads 61 a.     -   Outer cutter housing 50 having central bore 53, threads 52, and         at least one blade slot 51 extending through said housing 50,         wherein said at least one blade slot 51 is oriented         substantially perpendicular to the longitudinal axis of central         bore 53.     -   Elongate central mandrel 10 having upper threads 11, lower         threads 12, upper body section 15 having a substantially square         outer profile, and lower body section 14 having a substantially         round outer profile (that is, body section 14 has a         substantially cylindrical shape).     -   Elongate tapered blade mounting member 20 having a larger         diameter at its upper end than at its lower end, at least one         blade slot 22 disposed along the outer surface of said elongate         blade mounting member 20, and threads 21.     -   At least one blade holder assembly 30, slidably disposed within         said at least one blade slot 22 of tapered blade mounting member         20.     -   Bottom housing 40 having central bore 43, threads 42 and rounded         bottom bull nose profile 41.

FIG. 4A depicts a side sectional view of an upper portion of cutting assembly 100 of the present invention in a pinned, extended configuration concentrically disposed within the internal bore of pipe section 200. FIG. 4B depicts a side sectional view of a lower portion of cutting assembly 100 of the present invention in a pinned, extended configuration concentrically disposed within the internal bore of pipe section 200. It is to be observed that pipe section 200 can be production tubing, drill pipe, casing or other tubular good to be cut.

Referring to FIGS. 4A and 4B, cap member 1 is threadably connected to upper helical cam sleeve 80 having lower curved helical surface 81. Lower helical cam sleeve 90, having upper curved helical surface 91, is disposed below upper helical cam sleeve 80. Lower helical cam sleeve 90 is threadably connected to outer cutter housing 50 having at least one blade slot 51 (not visible in FIG. 4B) extending through the side wall of said housing 50: Lower outer housing 40 having central bore 43 and bottom bull nose profile 41 is threadably connected to outer cutter housing 50. Upper stem guide bushing 70 having central bore 73 is disposed within central bore 83 of upper helical cam member 80 and is threadably connected to lower stem guide bushing 60 having central bore 63 which, in turn, is disposed within central bore 93 of lower helical cam member 90.

Elongate central mandrel 10 has upper threaded connection 11, upper body section 15 (having a substantially square outer profile), lower body section 14 (having a substantially cylindrical outer profile) and lower threads 12. Upper body section 15 of elongate central mandrel 10 is slidably disposed within axial bore 2 having square profile in cap member 1. Cylindrical lower body section 14 of elongate central member 10 is slidably disposed within aligned central bore 63 of lower stem guide bushing 60 and central bore 73 of upper stem guide bushing 70. In the preferred embodiment, upper and lower stem guide bushings 70 and 60 are disposed within opposing upper and lower cam sleeves 80 and 90, and are provided to maintain concentricity of elongate central mandrel 10 within cutting assembly 100.

Lower threads 12 of elongate central mandrel 10 are connected to tapered blade mounting member 20. Elongate tapered blade mounting member 20, which partially extends into central bore 43 of lower outer member 40, has a larger diameter at its upper end 20 a than at its lower end 20 b. At least one blade slot 22 is disposed along the outer surface of said elongate blade mounting member 20, and are oriented substantially parallel to the longitudinal axis of said blade mounting member 20. Blade holder assemblies 30 are slidably disposed within said blade slots 22.

Still referring to FIGS. 4A and 4B, upper shear pin 120 is received within aligned transverse bore 2 of cap member 1 and transverse bore 13 of elongate central mandrel 10, thereby preventing elongate central mandrel 10 from moving axially relative to cap member 1. Similarly, middle shear pin 130 is received within aligned transverse bore 82 of upper helical cam sleeve 80 and transverse bore 74 of upper stem guide bushing 70, thereby preventing upper helical cam sleeve 80 from moving axially relative to upper stem guide bushing 70. Lower shear pin 140 is received within aligned transverse bore 92 of lower helical cam sleeve 90 and transverse bore 64 of lower stem guide bushing 60, thereby preventing lower helical cam sleeve 90 from moving axially relative to lower stem guide bushing 60.

FIG. 5 depicts a side perspective view of pipe cutting assembly 100 of the present invention in an unpinned, collapsed configuration, while FIG. 6 depicts a side perspective view of said pipe cutting assembly 100 rotated 180 degrees from the view depicted in FIG. 5. In FIGS. 5 and 6, upper shear pin 120 is sheared, thereby allowing elongate central mandrel 10 to move axially relative to cap member 1. Middle shear pin 130 is also sheared, thereby permitting upper helical cam sleeve 80 to move axially relative to upper stem guide bushing 70. Lower shear pin 140 is likewise sheared, permitting lower helical cam sleeve 90 to move axially relative to lower stem guide bushing 60. Blades 32 protrude radially outward, extending through blade slots 51 of outer cutting housing 50.

FIG. 7A depicts a side sectional view of an upper portion of cutting assembly 100 of the present invention in an unpinned, collapsed configuration along line 7-7 of FIG. 6, while FIG. 7B depicts a side sectional view of a lower portion of said cutting assembly 100 along line 7-7. Cap member 1 is threadably connected to upper helical cam sleeve 80 having lower curved helical surface 81. Lower helical cam sleeve 90, having upper curved helical surface 91, is disposed below upper helical cam sleeve 80. Lower helical cam sleeve 90 is threadably connected to outer cutter housing 50 having at least one blade slot 51 extending through the side wall of said housing 50. Lower outer housing 40 having bottom bull nose profile 41 is threadably connected to outer cutter housing 50, and is depicted as sitting on top of cement plug 202 disposed within tubing 200. Upper stem guide bushing 70 is disposed within central bore 83 of upper helical cam member 80 and is threadably connected to lower stem guide bushing 60 which, in turn, is disposed within central bore 93 of lower helical cam member 90.

Elongate central mandrel 10 has upper threaded connection 11, upper body section 15 (having a substantially square outer profile), lower body section 14 (having a substantially cylindrical outer profile) and lower threads 12. Upper body section 15 of elongate central mandrel 10 is slidably disposed within square axial bore 2 of cap member 1 and is prevented from rotation due to said mating square profiles. Cylindrical lower body section 14 of elongate central member 10 is slidably disposed within aligned central bore 63 of lower stem guide bushing 60 and central bore 73 of upper stem guide bushing 70.

Lower threads 12 of elongate central mandrel 10 are connected to tapered blade mounting member 20. Elongate tapered blade mounting member 20, which is depicted in FIGS. 7A and 7B extending into central bore 43 of lower outer member 40, has a larger diameter at upper end 20 a than at lower end 20 b. At least one blade slot 22 is disposed along the outer surface of said elongate blade mounting member 20, with a blade holder assembly 30 slidably disposed within each such blade slot 22.

FIG. 8 depicts a sectional view of retracted radial blade holder assemblies 30 of the present invention along line 8-8 of FIG. 4B. As depicted in FIG. 8, said blade holder assemblies 30 are positioned near the bottom portion 20 b of tapered blade mounting member 20. As a result, tips 32 a of blades 32 do not fully extend outward through blade slots 51 beyond the outer surface of cutter housing 50, and do not contact inner surface 201 of pipe 200. In the preferred embodiment, the portion of blade holder assemblies 30 extending into blade slots 22 can be flared or have a “T”-configuration to mate with a corresponding profile of said slots 22 in order to permit axial movement within said slots, while preventing such blade holder assemblies 30 from falling out of said slots 22

FIG. 9 depicts a detailed sectional view of upper shear pin 120 highlighted in FIG. 4A. Upper shear pin 120 is received within aligned transverse bore 2 of cap member 1 and transverse pin bore 13 of elongate central mandrel 10, thereby preventing elongate central mandrel 10 from moving axially relative to cap member 1.

FIG. 10 depicts a detailed sectional view of middle shear pin 130 highlighted in FIG. 4A. Middle shear pin 130 is received within aligned transverse bore 82 of upper helical cam sleeve 80 and transverse pin bore 74 of upper stem guide bushing 70, thereby preventing upper helical cam sleeve 80 from moving axially relative to upper stem guide bushing 70.

FIG. 11 depicts a detailed sectional view of lower shear pin 140 highlighted in FIG. 4A. Lower shear pin 140 is received within aligned transverse bore 92 of lower helical cam sleeve 90 and transverse pin bore 64 of lower stem guide bushing 60, thereby preventing lower helical cam sleeve 90 from moving axially relative to lower stem guide bushing 60.

FIG. 12 depicts a sectional view of extended radial blades 32 of blade holder assemblies 30 of the present invention along line 12-12 of FIG. 7B. As depicted in FIG. 12, said blade holder assemblies 30 are positioned near the upper portion 20 a of tapered blade mounting member 20 having a larger diameter than lower portion 20 b. As a result, blades 32 extend outward through slots 51 beyond the outer surface of cutter housing 50, thereby contacting with pipe 200.

FIG. 13 depicts a detailed sectional view of a portion of sheared upper pin 120 highlighted in FIG. 7A received within transverse pin bore 2 of cap member 1. Said pin 120 is being depicted as being sheared due to the axial movement of elongate central mandrel 10 relative to cap member 1.

FIG. 14 depicts a detailed sectional view of portions of upper shear pin 120 and middle shear pin 130 highlighted in FIG. 7A. A portion of upper shear pin 120 has been sheared and axially displaced from its original position due to the axial movement of elongate central mandrel 10. Similarly, a portion of middle shear pin 130 has been sheared and axially displaced from its original position due to the axial movement caused by opposing helical cam sleeves of the present invention.

FIG. 15 depicts a detailed sectional view of lower shear pin 140 highlighted in FIG. 7A. Lower shear pin 140 has been sheared and axially displaced from its original position due to the axial movement of caused by opposing helical cam sleeves of the present invention.

In operation, cutting assembly 100 of the present invention can be conveyed into a well or other environment containing pipe, casing, production tubing or other tubular goods to be cut. Although said cutting assembly 100 can be conveyed into a well on continuous tubing or electric line, it is to be observed that the cutting assembly of the present invention can also be conveyed and actuated using slickline or other non-conductive wireline, thereby greatly improving the versatility and cost-effectiveness of the present invention. As set forth herein, the present invention is described as being used to cut tubing, such as production tubing; however, it is to be observed that this description is illustrative only and is not to be construed as limiting in any way because cutting assembly 100 of the present invention can be used to cut many different types of pipe such as casing, drill pipe and/or other tubular goods.

In most cases, a gauge or “dummy” run will be made prior to running cutting assembly 100 into a well to ensure that said cutting assembly 100 can fully advance in the well to the depth of a desired cut; that is, to ensure that cutting assembly 100 will not become stuck in a “tight spot” or other area of restricted internal diameter while being conveyed into a well.

Following a successful gauge run, a plug is typically set within tubing to be cut at a desired distance below the location of a desired cut. Such plug can be cement deposited within the tubing (such as, for example, cement plug 202 depicted in FIG. 7B), including cement deposited as part of plugging and abandonment operations. Alternatively, said plug can be a mechanical plug set separately, or even a plug or anchor assembly conveyed along with and integrally attached to cutting assembly 100 of the present invention.

In the preferred embodiment, cutting assembly 100 is installed below at least one set of “jars”, which are well known to those having skill in the art. Such jars can be used to provide down-hole axial loading, typically in the form of concentrated jarring or forceful impacts, on tools or other components conveyed via wireline. Cutting assembly 100 is conveyed into the well to a desired depth in a pinned, extended configuration, as depicted in FIGS. 1 and 2. If needed, grease or other lubricant can be placed on the outer surfaces of the cutting assembly 100.

After cutting, assembly 100 is conveyed into a well to a desired depth, the jars are actuated to shear upper shear pin 120, which permits central mandrel 10 to move axially relative to cap member 1. Said jars are actuated again to shear middle shear pin 130, which permits upper helical cam sleeve 80 to move relative to upper stem guide bushing 70. Said jars are actuated yet again in order to shear lower shear pin 140, thereby permitting lower helical cam sleeve 90 to move relative to lower stem guide bushing 60. In the preferred embodiment, shear pin 120 is set to shear at less force than both middle shear pin 130 and lower shear pin 140. Similarly, middle shear pin 130 is also set to shear at less force then lower shear pin 140. Said shear pins 120, 130 and 140 can be made of brass or other material exhibiting desired characteristics.

As central mandrel 10 is forced downward, elongate tapered blade mounting member 20 extends into central bore 43 of lower outer member 40. Blade holder assemblies 30 slide within said blade slots 22, eventually becoming positioned near upper portion 20 a of tapered blade mounting member 20. Due to the relatively large diameter of upper portion 20 a of tapered blade mounting member 20, blades 32 protrude outward through slots 51 and extend beyond the outer surface of cutter housing 50 and make contact with the pipe 200 to be cut.

As the jars are actuated, upper helical cam sleeve 80 and lower helical cam sleeve 90 contact one another. Specifically, lower curved surface 81 of upper helical cam sleeve 80 contacts upper curved surface 91 of lower helical cam sleeve 90. Axial forces acting upon coaxially aligned upper and lower cam sleeve components allows opposing curved cam surfaces 81 and 91 to contact and rotate against each other; the helical cam tracks of sleeves 80 and 90 are designed such that axial movement between said cam sleeve components causes a corresponding relative rotational movement.

As opposing cam sleeves 80 and 90 convert such axial force to rotation and force, torque is imposed on elongate central mandrel 10. In other words, because square profile of upper section 15 of central mandrel 10 mates with (and is prevented from rotating within) axial bore 3 of cap 1, torque is transferred to elongate central mandrel 10. Such torque is in turn transferred to extended blades 32 which protrude through slots 51 in outer blade housing 50 and contact pipe 200. As said blades 32 are rotated, blades 32 cut into pipe 200.

In the preferred embodiment a combination of blades 32 make at least one complete revolution around the diameter of pipe 200 to be cut. Put another way, at least one revolution is made so that the entire circumference of pipe 200 is cut.

After pipe 200 has been successfully cut, cutting assembly 100 retrieved using upward force from a slickline or other wireline unit. Such upward force moves elongate central member 10 upward, which in turn pulls tapered member 20 upward and out of central bore 43 of bottom housing 40. As a result, blade holder assemblies 30 slide within slots 22, eventually being positioned near lower end 20 b of tapered blade mount member, resulting in retraction of blades 32 inward. Said blades 32 retract within slots 51, and do not extend beyond the outer surface of outer blade housing 50 (and, therefore, do not contact pipe 200).

With blades 32 in a retracted position, cutting assembly 100 can be pulled out of the well. Thereafter, pipe 200 above the location of such cut can be retrieved from the well for subsequent salvage or disposal.

The above-described invention has a number of particular features that should preferably be employed in combination, although each is useful separately without departure from the scope of the invention. While the preferred embodiment of the present invention is shown and described herein, it will be understood that the invention may be embodied otherwise than herein specifically illustrated or described, and that certain changes in form and arrangement of parts and the specific manner of practicing the invention may be made within the underlying idea or principles of the invention. 

1. A pipe cutting apparatus comprising: a) a housing having a central bore extending therethrough; b) an elongate mandrel having a first end and a second end, slidably disposed in said central bore of said housing; c) a tapered mounting member connected to said second end of said elongate mandrel, having at least one elongate slot oriented substantially parallel to the longitudinal axis of said tapered mounting member; d) at least one blade slidably disposed in said at least one elongate slot; e) a first helical cam member; and f) a second helical cam member, wherein axial force applied to said first and second cam members causes said at least one blade to rotate.
 2. A pipe cutting apparatus comprising: a) a cap member having a central bore extending therethrough; b) an elongate mandrel having a first end and a second end, slidably disposed in said central bore of cap member; c) a tapered mounting member connected to said second end of said elongate mandrel, having at least one elongate slot oriented substantially parallel to the longitudinal axis of said tapered mounting member; d) at least one blade slidably disposed in said at least one elongate slot; e) an upper cam sleeve having a lower helical surface, connected to said cap; and f) a lower helical cam sleeve having an upper helical surface, wherein said lower helical surface of said upper cam sleeve rides on the upper helical surface of said lower cam sleeve.
 3. The apparatus of claim 2, wherein said central bore extending through said cap member is square, and the portion of said elongate mandrel disposed through said bore has a square cross section.
 4. The apparatus of claim 2, further comprising a shear pin disposed through aligned transverse bores in said cap member and elongate mandrel.
 5. The apparatus of claim 2, further comprising a blade housing having at least one slot extending therethrough, wherein said blade housing is connected to the bottom of said lower helical cam sleeve, and said at least one blade is aligned with said at least one slot.
 6. The apparatus of claim 5, further comprising a base member having a top and a bottom, wherein said bottom forms a bull nose and said top is connected to said blade housing.
 7. The apparatus of claim 2 further comprising at least one stem guide bushing disposed around said elongate mandrel.
 8. A method for cutting pipe in a well comprising the steps of: a) conveying a pipe cutting apparatus inside said pipe to a desired depth; b) applying axial force to said pipe cutting apparatus; c) extending at least one blade radially outward from said pipe cutting apparatus to contact said pipe; d) applying axial force to said pipe cutting apparatus to rotate said at least one blade in a direction substantially perpendicular to the longitudinal axis of said pipe; e) retracting said at least one blade within said pipe cutting apparatus; and f) retrieving said pipe cutting apparatus from said well.
 9. The method of claim 8, wherein said axial force is applied to said pipe cutting apparatus using jars.
 10. The method of claim 8, further comprising the step of shearing a pin prior to extending said at least one blade.
 11. The method of claim 8, further comprising the step of shearing a pin prior to rotating said at least one blade. 